1. Field of the Invention
The present invention relates to a clamping element freewheel, in particular a damped clamping element freewheel with a cage, wherein the freewheel is useable, e.g., on an output side of a crank continuously variable transmission. The invention also relates to a crank continuously variable transmission (CVT) with a freewheel of this type.
2. Description of the Related Art
A crank CVT is known, e.g., from EP 1 650 071 A2. An input shaft that is drivable by an engine, and which forms an input shaft for a transmission, is provided with an adjustable eccentric drive arrangement with eccentric components. The drive arrangement is connected to a driven shaft through a rod shaped connection elements, wherein the driven shaft forms an output shaft for the transmission. The driven shaft is driven to rotate by transferring the stroke of the connection elements through freewheel devices to the driven shaft, and thus the output side of the transmission. The freewheel devices are provided between the rod shaped connection elements and the driven shaft.
In that crank CVT, the driving crankshaft and the output shaft, or the driven shaft, are aligned parallel to one another and rotatably supported in a transmission housing. When torque is introduced by an internal combustion engine into the crankshaft, the torque is transmitted through the crank CVT to the output shaft. Depending on the position of the eccentric components with respect to the rotation axis of the drive shaft, the eccentricity of the eccentric components, and thus their rotation axis relative to the drive shaft, is changed, which facilitates adjusting the stroke transferred from the connecting rod shaped connecting element to the drive shaft, and thus the transmission ratio of the transmission. At the output shaft the torque can be captured, e.g., for driving wheels of a vehicle. Typically, plural eccentric units are arranged in the crank CVT in the axial direction of the crankshaft behind one another, at which respective connecting rod shaped connection elements are attached, and which are connected with a respective number of freewheel units on the output side of the transmission, wherein the freewheel units on the output shaft are also arranged behind one another in the axial direction.
Two basic types of freewheels are known, namely shiftable freewheels that selectively block a relative rotation of an outer ring and an inner ring in one of the two directions of relative rotation as a function of a shifting position, and freewheels that have a fixed and not variable blocking device, in which they prevent a relative rotation between an outer ring and an inner ring, while a relative rotation of the outer ring and the inner ring is facilitated in another direction of relative rotation. In shiftable freewheels, e.g., in order to implement a reverse gear no additional transmission and no separate engine has to be provided since shifting the freewheels facilitates changing the rotation direction of the output shaft relative to the rotation direction of the input shaft of the transmission. For non-shiftable freewheels, either a separate motor, e.g., an electric motor, is provided, or another transmission is coupled subsequent to the output shaft of the transmission, e.g., a planetary transmission that is part of the load transfer path in the transmission when required, namely when a reverse driving function is to be provided and which is otherwise decoupled.
Shiftable freewheels are typically configured as roller freewheels in which rollers roll off between an inner ring and an outer ring, and are pressed through suitable spring loading into a clamping gap in one or another relative direction of rotation. Thus, at least one of the inner ring or the outer ring has a profile so that the clamping gap is generated.
As an alternative to the rolling element freewheels, clamping element freewheels are known that are more compact and lighter than rolling element freewheels. In the clamping element freewheels the clamping elements are profiled, e.g., so that they block the relative rotation of the inner ring or outer ring in one position, wherein the inner ring and the outer ring can have circular cross sections and block the relative rotation in another position.
In freewheels, the position of the clamping or rolling elements in which the clamping or rolling elements block the inner ring and the outer ring relative to one another is designated as the clamping or blocking position, in which the rolling or clamping elements are disposed in a clamping gap formed between the inner ring and the outer ring. The position in which they facilitate a rotation of the inner ring and the outer ring relative to one another is designated as the freewheeling position. This language is used in the instant description also for clamping element freewheels, in which the blocking or release is a function of a currently effective diameter of the clamping elements and not of a position of the clamping elements along the circumferential direction.
Thus, it is an object of the present invention to provide a clamping element freewheel, in particular for a crank CVT, which has a robust configuration and operates reliably.